Instrument for measuring home cooking skills in primary health care

ABSTRACT OBJECTIVE To develop and validate an instrument for measuring the home cooking skills of health professionals involved with guidelines for promoting adequate and healthy food in primary health care. METHODS This is a methodological study with a psychometric approach, carried out in the city of São Paulo between January and November 2020, to develop and validate a self-applied online instrument. The data of the 472 participants were presented by descriptive statistics. Content validation was performed by expert judgment using the two round Delphi technique and empirical statistics for consensus evidence. Exploratory factor analysis was used for construct validation and reliability analysis, and the model adjustment rates and composite reliability were analyzed. RESULTS The instrument presented satisfactory content validity for CVRc indices and 𝜅 in the two rounds of the Delphi technique. After the factor analysis, the final model of the Primary Health Care Home Cooking Skills Scale presented 29 items with adequate factorial loads (> 0.3). Bartlett’s and Kaiser-Meyer-Olkin’s (KMO) tests of sphericity performed in exploratory factorial analysis suggested interpretability in the correlation matrix, the parallel analysis indicated four domains and explained variance of 64.1%. The composite reliability of the factors was adequate (> 0.70) and the H-index suggested replicable factors in future studies. All adjustment rates proved to be adequate. CONCLUSIONS The Primary Health Care Home Cooking Skills Scale presented evidence of validity and reliability. It is short and easy to apply and will make it possible to reliably ascertain the need for qualification of the workforce, favoring the planning of actions and public policies of promotion of adequate and healthy food in primary health care.


INTRODUCTION
Home cooking skills (HCS) comprise actions such as menu planning, selection, mixing, cutting and cooking of food, the ability to perform tasks whilst cooking and confidence for culinary practices 1 . They are related to environmental and economic implications 2 and are valued by the Guia Alimentar para a População Brasileira (Food Guidelines for the Brazilian Population) 3 as an expression of cultural and social aspects. The document recognizes cooking as a strategic practice to promote adequate and healthy food (AHF), aiming to reduce the choice of ultra-processed foods, which are associated with overweight, obesity, cancer and other diseases 4,5 . Therefore, recognition of cooking should be paramount in food and nutrition education actions 2 .
In Brazil, the guidelines of AHF are located substantially within the scope of primary health care (PHC), the first level of care and link of subjects with the Unified Health System. PHC professionals play a relevant role in promoting food and nutrition education actions involving culinary practices, such as dissemination of recipes, workshops, guided visits to open-air markets, home visits and sensory exploration of food 6 . Such actions allow health workers to convey technical knowledge to the daily lives of the subjects, therefore it is important that those workers develop their home cooking skills 7 .
An accurate diagnosis of these skills is essential to promote workforce qualification and plan public health actions and policies on the subject, and it relies on the use of valid and reliable instruments, based on robust psychometric criteria 8,9 . Teixiera et al. 10 identified and critically analyzed the psychometric quality of 12 Brazilian and international instruments for measuring cooking skills in adults. The psychometric attributes of those instruments were considered insufficient, with unsatisfactory results based on statistical criteria or methodological inadequacies. Two of the studies were Brazilian: Jomori 11 performed a cross-cultural adaptation of an instrument based on the program Cooking with a Chef, from Clemson University. The results of a part of the scale of this instrument were unsatisfactory for reliability. Martins et al. 12 developed a cooking confidence scale for parents of schoolchildren. The authors evaluated the internal consistency, stability and content validity of the instrument, but did not report agreement rates between experts and procedures for construct validity.
Thus, there is a strong need to develop a new instrument for assessing home cooking skills aimed at Brazilian health professionals involved with guidelines for promoting adequate and healthy food in PHC, based on psychometric criteria that follow methodological rigor to determine its validity and reliability recommended in the scientific literature.

METHODS
This is a methodological study with a psychometric approach 13 conducted between January and November 2020.
This study was approved by the research ethics committee of University of São Paulo (CAAE 15194819.8.0000.5421, No. 3,502,315) and by the co-participating institution of the São Paulo Municipal Health Department (SMS-SP) (No. 3,585,369). The participants were informed of the objectives of the study and confidentiality of the data through an informed consent form.
In the prototype stage, a working group was created with nine members of both sexes and from different Brazilian states (São Paulo, Mato Grosso, Pará and Minas Gerais). They were nutrition and gastronomy majors from the Faculdade de Saúde Pública of Universidade de São Paulo (FSP-USP) involved with culinary approach disciplines and PhD researchers with experience in the elaboration and validation of research instruments to systematically develop the instrument.
To define the theoretical domains and items of the first version of the instrument proposed in this study, the following were considered: (a) professional experience and culinary experience of the group; (b) exploration of theoretical framework on HCS 14 (c) systematic review to identify and analyze psychometric properties of instruments that assessed the home cooking skills of adults 10 . The domains, items and response formats of the instruments identified in this review were discussed by the research group for the construction of the prototype.
The construction of the initial set of items and response formats of the prototype version of the instrument, entitled Primary Health Care Home Cooking Skills Scale (PHCHCSS), followed the quality recommendations proposed by DeVellis 15 .
The next phase, the psychometric phase, consisted of three stages. The first stage featured experts from various professional levels, including university professors, researchers and nutrition and gastronomy professionals from Brazil 16 . A number of participants between three and 10 was considered sufficient 17 .
The two-round Delphi method 18 was used. Experts completed online questionnaires, with semi-structured questions of sociodemographic characterization and evaluation of the items and theoretical domains of the instrument built in the prototype phase. They proposed improvements, inclusion and exclusion of items, adequacy of the options of the instrument scale, and responded to a scale Likert of agreement (1 = strongly disagree and 4 = strongly agree) to evaluate each item for: • Clarity: Was the item written in such a way that the concept is understandable and adequately expresses what is to be measured?
• Pertinence: Does the item reflect the concepts involved in the domain and is it adequate to achieve the proposed objectives?
• Relevance: Is the item important for the construction of the domains that are the focus of the research scale?
The first round of the panel took place between March 26 and April 29, 2020 and featured eight experts. The research group assessed the comments provided, excluded irrelevant and non-pertinent items, made adjustments to those considered unclear and included suggested items for a better coverage of the phenomenon. The instrument was re-submitted to the experts for evaluation after the modifications. Second round, started on May 28, 2020, lasted 30 days and featured seven experts.
The characteristics of the study participants were presented by descriptive statistics. The Critical Content Validity Ratio -CVRc was used to statistically analyze the validity of each attribute of the items and domains 19 and the Kappa coefficient (k) was calculated to evaluate the agreement between experts on each item 20 of the two rounds of the panel. Items with CVRc > 0.05 and k ≥ 0,60 20 were retained 19 . The content validity index (CVI) was also used to analyze the validity of the instrument as a whole 21 . The result > 0.8 was considered acceptable 22 .
The second stage was the pre-test phase, in which professionals from a health center in the city of São Paulo, with similar characteristics to the research population of the project, tested the usability of PHCHCSS. The pre-test participants were not part of the construct validity sample and reliability analysis of the instrument. They commented on possible difficulties in filling out the instrument, clarity and adequacy of the questions to the objective of the research and recorded response times.
In the third stage, construct validity and reliability of PHCHCSS were tested. The scale was developed for professionals involved in the promotion of adequate and healthy nutrition in basic health units (BHU) of São Paulo's Municipal Health Department (SMS-SP). There are 464 BHU in the city of São Paulo 23 .
The sample included professionals who expressed their consent to participate. Recruitment was done by contacting regional health coordinators, technical health supervisors and BHU managers to collect the emails addresses of target professionals. A website was also developed a , advertised on social media to present and clarify the purpose of the research and to recruit participants. The number of participants in the sample was based on the recommendations of Costello and Osborne 24 , of 10 subjects per instrument item.
Data collection began on August 2, 2020, lasting 30 days. A total of 472 professionals answered a sociodemographic questionnaire and PHCHCSS online. Their characteristics were presented by descriptive statistics.
Exploratory factor analysis (EFA) was used to evaluate the factorial structure of the PHCHCSS. Polychoric correlation and the Robust Diagonally Weighted Least Squares (RDWLS) extraction method were used. The decision on the number of retained factors was made by parallel analysis with random permutation of the observed data 25  To test the reliability, the composite reliability (CR) was calculated, with acceptable values > 0.70 32 .
All statistical analyses were performed using the statistical software Factor, version 10.10.03 29 .

RESULTS
The Box presents details on the theoretical domains and the construction of a set of items of the prototype version of the PHCHCSS based on the discussions of the research group, exploration of the theoretical framework and systematic review. Forty-four items were proposed to evaluate the home cooking skills of PHC professionals, with response options structured into a five-point Likert-type scale (0 = strongly disagree and 5 = strongly agree).
The instruments identified in a systematic review had dimensions of planning, selection and purchase of food and confidence in food preparation, and may or may not include pre-prepared and convenience products.
For the PHCHCSS, the theoretical dimensions of HCS for the construction of the initial items were considered to be the food shopping planning and meal preparation, culinary creativity, the use of sensory perception and confidence in the preparation of meals based on fresh, minimally processed and culinary ingredients, as recommended by the Guia Alimentar para a População Brasileira. Multitasking skills were also identified as a theoretical domain. are defined in the scientific literature as the ability to perform tasks simultaneously in the home environment, representing an advantage when preparing meals.
The prototype version of the instrument was submitted to content evaluation by experts.
The main results of the development and validation of the PHCHCSS are shown in the Figure     In the psychometric phase, the first stage was the validation of the content. The study sample size was adequate for this stage. The response rate for the first round of the Delphi technique was 72.7% (8/11) and 87.5% (7/8) for the second round. Most of the experts were female (n = 7; 87.5%), with a mean age of 42.3 years (SD = 9.0). Of the total, 37.5% (n = 3) were experts (latu sensu), 12.5% (n = 1) masters, 25% (n = 2) PhDs and 12.5% (n = 1) full professors. The panel also had a lay participant (n = 1; 12.5%) with training in gastronomy and a full-time job cooking. The experts were professors at public (25%) and private (12.5%) universities, researchers (12.5%), nutritionists in food services (37.5%) and culinary  (3) Neither agree nor disagree, (4) Agree, (5) Strongly agree. This response scale was changed to a frequency scale at the suggestion of the experts after Round 1. Experts reported that the respondents found it difficult to understand the agreement scales. In addition, agreement scales can indicate the individual's perception of their skills, but they do not necessarily reflect the behaviors that make it possible to actually measure such skills. In this case, the adequacy for a frequency scale was shown to be more consistent with the objective of this instrument. The amendment was approved by the experts who took part in Round 2. The new scale is presented as follows: (1) Never, (2) Almost Never, (3) Sometimes, (4) Almost always, (5) Always. The authors made minimal changes to the labels and questions of the instrument (without changing their objectives) to make them coherent with the new response scale. Those changes were also approved by the experts. d Items excluded by the researchers with the consent of the expert group after consultation in the second stage of the panel. The item Buy food at food markets was excluded considering that one can shop for food in other places, not only food markets, and that this subject was included in other items of the instrument; item Quickly desalt dried meat in boiling water was excluded considering that the purpose of the instrument is to measure the cooking skills for preparing daily meals (dried meat is not consumed on a daily basis in the city of São Paulo) and, considering the frequency label, there could be an interpretation bias on the part of respondents (respondents could inform the frequency with which they prepare dried meat without desalting it); Prepare homemade feijoada from the scratch was excluded considering that the purpose of the instrument is to measure cooking skills for preparing everyday meals (feijoada, though a typical Brazilian dish, is not prepared every day in the city of São Paulo) and, considering the frequency label, there could be an interpretation bias on the part of respondent (respondents could inform the frequency with which they cook feijoada and not if they make it from scratch). e Justification not presented by the expert or not accepted by the author. Although the CVRc were slightly lower than the critical reference limit for the relevance attribute 19 , the item was kept in view of the value of agreement among experts on the item and to ensure the coverage of the domain. We chose to keep the item and investigate its behavior in factor analysis. f New items, submitted to content validity analysis (clarity, pertinence, relevance and agreement among experts) in the second Round of the panel of experts. The themes included in the added items comprised suggestions from experts in the first Round, to expand the scope of the domains. Continue professionals (12.5%). The length of professional experience ranged from 10 to 33 years (mean = 17.8 years; SD = 7.9 years). The average time devoted to culinary practices among experts was 12.2 hours per week (SD = 9.6 hours per week).
The evaluation of the experts resulted in the exclusion of seven items from the prototype version of the instrument, two items transferred from their original domains, three items revised for clarity, six new items proposed and a change from the agreement scale to a frequency scale, totaling 43 valid items for content. An overview of the content validity analysis of the instrument is shown in Table 1.
The second stage, pre-test, was conducted by five professionals from a health center in the city of São Paulo. The covid-19 pandemic posed an obstacle for recruitment, given the intensified demand for care at BHU. The sample was composed of women who worked as nutritionists (n = 3; 60%), psychologists (n = 1, 20%) and nurses (n = 1; 20%). This sample was not part of the validity and reliability analysis of the instrument. Participants reported that the instrument was easy to access by computer, comprehension of the questions and answer options, with a suggestion to enlarge the font size of the questions, which was adopted by the research group. The average response time was 15 minutes.

Continue
The third stage consisted in performing construct validity and reliability analysis. The study sample size was adequate for this stage. Table 2 shows the characteristics of the 472 health professionals from the participating PHC.  The final EHAPS model resulted in a scale of the type Likert, with response options on the frequency of actions centered on HCD attributes, with 29 items b . The scale score is determined by the sum of the scores corresponding to the options indicated in each item ("never" = 0, "almost never" = 1, "sometimes" = 2, "almost always" = 3 and "always" = 4). Based on the sum of points of the items, four score ranges were proposed with the following statuses: low HCS (0 to 29 points, equivalent to ≤ 25% of the maximum score); moderately low HCS (30 to 58 points, equivalent to > 25% and ≤ 50% of the maximum score); moderately high HCS (59 to 87 points, corresponding to > 50% and ≤ 75% of the maximum score) and high HCS (88 to 116 points, or > 75% of the maximum score). The interpretation of the final score was graphically presented in a ruler format with color gradation (from intense red, representing low HCS, to intense green, representing high HCS), with instructional messages about the score achieved and encouragement to the development of these skills. Table 3 shows the sequence of item reduction by EFA. The factorial loads of the retained items, composite reliability indexes and replicability estimates of the factor scores (H-index) are shown in Table 4. Names and descriptions of the construct measured by each factor extracted in the EFA are also reported based on the interpretation of the items retained. These factors were understood as dimensions of home cooking skills assessed by the PHCHCSS.
The items retained showed adequate loads in their respective factors. No new patterns of cross loads were found in the reduced model (i.e. items with factorial loads > 0.30 in more than one factor). The composite reliability of the factors was adequate (> 0.70) for all factors. The H-index measure suggested replicable factors in future studies (H > 0.80) 28 .

DISCUSSION
This study reported the development of an instrument to measure the home cooking skills of primary health care professionals in the city of São Paulo. The psychometric methodology proved to be appropriate to analyze the reliability and validity of the PHCHCSS.
Although uncommon in scale development studies, the content validity stage had a lay member in the the expert panel 33 . The inclusion of this member allowed identifying and correcting potential problems in the scale in advance of its application for data collection for exploratory factor analysis 8 . The application of the strict consensus method with two measures (CVRc and k) to quantify the degree of agreement among experts resulted in items with strong content validity. The opinion of experts was considered in other studies that reported instruments for measuring cooking skills 12,34 . However, these studies did not present empirical methods derived from the judgment of experts as evidence of the content validity. does not in itself provide relevant information for the validation process 13,28 . Thus, this study stands out regarding the methodological rigor employed for content validity of the PHCHCSS.
The pre-test participants reported adequate usability of the instrument. Five health professionals participated in this stage. Rattray et al. 35 assert that pilot studies can be conducted with small samples as long as the performance of the analyses is not compromised in any way. Considering that the sample was used to qualitatively evaluate the understanding and deployment of the instrument, the number of pre-test professionals did not create limitations to the study.
Regarding the stage of construct validity and reliability of the PHCHCSS, the parallel analysis suggested a multidimensional instrument with four factors. The multidimensionality of the scale is aligned with the complex nature of the acts of eating and cooking, recognized by the Guia Alimentar para a População Brasileira 3 .
The creative planning dimension considers creativity when planning and preparing home-cooked meals in natura, minimally processed foods and procedures done in advance to facilitate the act of cooking. A similar finding was observed in the study by Jomori 11 , which considers the creative ability to plan menus and organize meal preparation as skills for individual-centered culinary practice. This dimension is related to the main recommendation of the Guia Alimentar para a População Brasileira 3 : "You should always prefer in natura or minimally processed foods and culinary preparations to ultra-processed foods". It is also related to the chapter on understanding and overcoming obstacles to putting this and other recommendations into practice. Cooking procedures done in advance shorten the time spent preparing meals. Given the pace of modern life, this obstacle is more easily overcome when multitasking skills are also put into practice.
The dimension of multitasking skills comprises the ability to perform household tasks simultaneously to culinary practices. If an individual is unable to cook while doing laundry and taking care of children, they may be less likely to prepare a home-cooked meal 36 . Gabe 37 discusses the influence of the home environment on the quality of the meals consumed, highlighting that there is a gender discrepancy regarding responsibility for household chores, which is reinforced by Mills et al. 38 These findings provide an opportunity to use the PHCHCSS in studies aimed at analyzing differences in multitasking skills between genders, in order to encourage the fair sharing of responsibilities in the home, which includes preparing meals.
The dimension of confidence regarding cooking skills corresponds to self-sufficiency to employ cooking techniques and utensils. According to Martins 12 , the confidence judgment considers individual performance, which depends on practice and task performed, considered an excellent predictor of behavior to determine how individuals employ their skills. The PHCHCSS reduces misinterpretations about HCS by disregarding questions about confidence to prepare meals based on ready-made and convenience products, which could overestimate the individual's skills, a recurring problem in international instruments 1 . The cooking confidence scale by Lavelle et al. 34 , for example, includes questions about confidence to "prepare food in a microwave oven, including heating ready-made dishes".
Finally, the dimension of food selection, combination and preparation refers to the sensory and quantification aspects of food aiming at the adequacy of purchasing and cooking procedures. Similar components, which concern the ability to shop for food, use it in preparations and judge it for quality, are found in the study about food literacy by Vidgen and Gallegos 39 . According to the authors, low food literacy is associated with increased diet-related chronic diseases.
The results of the exploratory factor analysis showed adequate factorial loads and commonalities in all items retained in the instrument 27,28 and they suggest a welldefined latent variable, with dimensions that are likely to be stable in future studies 31 . The adjustment indexes presented validated the model extracted from the analysis and confirm the measured theory, showing a well-defined construct 30 . The reliability of the instrument was also adequate, with satisfactory results of composite reliability. This measure represents a good indicator to evaluate the quality of the structural model of the instrument and is presented as a more robust precision indicator, compared to the alpha coefficient 32 .
Developing evaluation instruments is a complex task, only recommended in the lack of another instrument suitable to the reality being investigated 40 , which is the case in this study.
As an advantage, the PHCHCSS is short, easy to apply and standardized, allowing its use in comparative studies. This instrument summarizes the home cooking skills according to scoreranges easy to interpret, delimited by traffic light colors, based on a diagram suggested by Gabe 37 to interpret the score of her dietary quality assessment instrument, adopted by the Ministry of Health. It also offers messages on the status of the individual's home cooking skills, with instructions for encouraging and appreciating these skills. It should be noted, however, that the score of the scale derives from its raw score. Although commonly found in studies of instrument development, the use of this score assumes a subjective definition of classification cut-off points, conferring the same weight for items with different factorial loads. The item response theory is an analysis proposal to overcome this limitation by considering the characteristics of the questionnaire items regarding the ability to differentiate the variable of interest and location in the respective continuum and a probabilistic model to estimate and describe the scores 41 . Thus, the item response theory could be used in future studies aiming to improve the score of this instrument, validated by classical methods.
Automation minimized possible errors by the interviewer. The online application of the instrument proved advantageous due to its low cost and ease of access. However, its application on paper has not been studied to verify the occurrence of similar results, a limitation of this study. The printed version would allow access to health professionals working in places with limited internet access or not included digitally.
Another limitation is that a convergent validity study was not conducted. This kind of validity refers to the associations of the PHCHCSS score with external measures, which could confirm whether the scale measures HCS related to food choices recommended by the Guia Alimentar para a População Brasileira and could be performed by comparing the scale score with a 24-hour dietary recall or with the score of a food literacy scale. Conducting this validity study would be opportune in future analyses.
Finally, the sample used for exploratory factor analysis was composed of professionals working in primary health care in the city of São Paulo. Despite being the main destination for regional migration in Brazil 42 , the sample from this city may not represent the cultural diversity of food within the national territory. Thus, a cross-cultural adaptation of the instrument for Brazilian macroregions is recommended.
This study is innovative in the context of the recognition of cooking as an emancipatory practice and health promotion. It is understood mastering home cooking skills allows primary health care professionals to bring their scientific knowledge closer to people's lives and to social practices and knowledge, thereby strengthening the ability of individuals or communities to identify solutions for their daily lives. This instrument will make it possible to reliably ascertain the need for qualification of the workforce for actions to promote healthy and adequate food based on home cooking skills. It also provides opportunities to identify needs for reviewing pedagogical proposals of health courses, to train professionals to work on food sovereignty and the human right to adequate food at the expense of medicalizing practices and guidelines.